<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .sky{
            width: 100px;
            height: 160px;
            background-color: red;
        }
        .sky {
            position: absolute;
            left: 0;
            right: 0;
            top: 0;
            bottom: 0;
            margin: auto;
        }
        /*.sky{*/
            /*position: absolute;*/
            /*top: 50%;*/
            /*left: 50%;*/
            /*margin-top: -80px;*/
            /*margin-left:-50px ;*/
        /*}*/
    </style>
</head>
<body>
    <div class="sky">

    </div>
</body>
</html>